Systems and methods for disinfection

ABSTRACT

Methods and systems for establishing Taylor-Couette flow in a fluid are provide. Aspects of the disclosed methods and systems incorporate Taylor-Couette flow in combination with a source of radiation to provide more uniform radiation exposure to the fluid and its components. Common problems of non-uniform radiation levels and concentration boundary layer effects in UV reactors are largely eliminated using the methods and devices provided herein.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims benefit of U.S. Provisional PatentApplication No. 60/420,985 filed on Oct. 24, 2002, and to U.S.Provisional Patent Application No. 60/461,326 filed on Apr. 8, 2003,both of which are incorporated by reference in their entirety.

BACKGROUND

[0002] 1. Technical Field

[0003] The present disclosure is related generally to methods andsystems for moving fluids, more particularly, methods and systems forgenerating fluid flow that increases fluid exposure to an energy sourcefor sterilization or disinfection.

[0004] 2. Related Art

[0005] Water use is a major environmental concern and methods to reduceand reuse water consumption are in demand. In food processingfacilities, water shortages have made water reclamation and reuse anintegral component of environmental programs. To ensure that re-usedeffluents do not pose an unreasonable risk to public health, theEnvironmental Protection Agency (EPA) has outlined strict regulationsfor water reclamation. These water disinfection regulations provide asubstantial public health benefit by reducing discharges of manywaterborne pathogenic organisms to water supplies, recreational water,shellfish water and other waters that can potentially transmit diseaseto humans.

[0006] Many technologies exist for bacterial destruction in waterreclamation such as chlorination which is a relatively low costdisinfection process. Chlorine treatment, however, presents a number ofproblems. For example, chlorine disinfection is incapable of achievingappreciable inactivation of the several viruses and protozoa,specifically, Cryptosporidium parvum at reasonable disinfectant dosesand contact times (Sobsey, M. D. (1989). Inactivation of health-relatedmicroorganisms in water by disinfection processes. Wat Sci. Tech.21:179-195). In addition, large chlorine concentrations generatechloro-organic, disinfection by-products such as trihalomethanes (THMs)and other carcinogens that persist in the environment (Matsunaga, T.,and M. Qkochi. (1995). TiO ₂-Mediated Photochemical Disinfection ofEscherichia coli Using Optical Fiber. Environ. Sci. Technol.29:501-505).

[0007] Due to the environmental concerns associated with chemicaldisinfection, current water treatment methods are moving away fromtraditional chemical to physical procedures (Cho, I. H. et al. (2002).Disinfection effects E. coli using TiO ₂ AJV and solar light system.Wat. Sci. and Tech. 2: 181-190). For example, use of ultraviolet (UV)radiation is becoming more popular for wastewater treatment since it iseffective against both bacteria and viruses, leaves no residues and iseconomical (Wong, E. et al. (1998). Reduction of Escherichia coli andSalmonella senftenberg on pork skin and pork muscle using ultravioletlight. Food Microbiology. 15:415-423). UV processing uses radiation inthe germicidal range from 200 to 280 nm to generate DNA mutations withinpathogens (Federal Department of Agriculture and Center for Food Safetyand Applied Nutrition. (2000). Kinetics of microbial inactivation foralternative food processing technologies: Ultra-violet light). Thelatter study also concludes that to achieve microbial inactivation, theUV radiant exposure must be at least 400 J/m² in all parts of theproduct. Moreover, UV irradiation is particularly effective when it isused in conjunction with powerful oxidizing agents such as ozone andhydrogen peroxide.

[0008] Treatment of fluid flow is also important in food processing forexample in processing of beverages such as milk, juices, alcoholicdrinks or soft drinks. Existing methods for treating fluid foodstuffstypically include exposing the foodstuffs to high temperatures in aneffort to neutralize potentially harmful bacteria. Unfortunately,thermal treatment of foodstuff can cause the breakdown of ingredientsincluding proteins and vitamins. The United States Food and DrugAdministration (US-FDA) has recently published a ruling (21 CFR 179)that approves the use of UV radiation in place of pasteurization.

[0009] Early modeling of disinfection efficiencies in flow-through UVreactors focused on the ideal designs of either a completely mixed(stirred tank) or plug flow configurations (Haas, C. N. andSakellaropoulos, G. P. (1979). Rational analysis of ultravioletdisinfection reactors, Proceedings of the National Conference onEnvironmental Engineering, American Society of Civil Engineering,Washington, D.C.; Severin, B. F. et al. (1984) Kinetic modeling of UVdisinfection of water. Inactivation kinetics in a flow-through UVreactor, J WPCF. 56:164-169). As summarized by the Water EnvironmentFederation (Water Environment Federation (1996). Wastewater DisinfectionManual of Practice FD-10, chapter 7, Alexander, Va.), Scheible(Scheible, O. K. (1987). Development of a rationally based designprotocol for the ultraviolet disinfection process. J. Water PollutionControl Fed. 59:25-31) developed a model to account for non-idealreactor theory that requires four empirical constants. A strictlyempirical model was also proposed by Emerick and Darby (Emerick, R. W.and Darby J. L. (1993). Ultraviolet light disinfection of secondaryeffluents: predicting performance based on water quality parameters.Proc. Plann. Des. and Oper. Effluent Disinfection Syst. Spec. Conf.,Water Environment Federation, Whippany, N.J., p. 1 87) to account for anumber of factors that influence water quality. Recently, computationalfluid dynamic (CFD) solutions have provided insight into the turbulentflow characteristics of UV reactors (Lyn, D. A. et al. in E.R. (1999).Numerical Modeling of flow and disinfection in UV disinfection channels,J Environ. Eng. 125, 17-26).

[0010] Of the two ideal designs and considering a single reaction, it iswell established that plug flow provides comparable yield but with asubstantial reduction in holdup volume that can exceed two orders ofmagnitude compared to a completely mixed reactor (Levenspiel, O. (1972).Chemical Reaction Engineering, 2^(nd) Ed., John Wiley and Sons, Inc.,New York, N.Y.). For such plug flow designs, the surface-to-volume ratiois large which is favorable to the transmission of UV radiation throughthe reactor walls and contained fluid. The major limitations to plugflow designs, however, are both non-uniform radiation intensities withinthe fluid and low concentrations of absorbing species such as viablepathogens near irradiated walls. The effects of the latter are reducedby increasing the flow rate thus reducing the velocity and concentrationboundary layer thickness but, unfortunately, also the residence time andthus the radiation dosage.

[0011] Previous studies on the effects of radiation in Taylor-Couetteflow are the growth of algae (Miller, R. L. et al. (1964).Hydromechanical method to increase efficiency of a lgal photosynthesis,Ind. Engng. Chem. Process Des. Dev. 3:134) and the development of areactor for heterogeneous photocatalysis (Sczechowski, J. G. et al.(1995). A Taylor vortex reactor for heterogeneous photocatalysis, Chem.Eng. Sci. 50:3163).

[0012] Recently, the inventors herein (Forney, L. J., and Pierson J. A.,(2003), Optimum photolysis in Taylor-Couette flow, AIChE 1.49:727-733;Forney, L. J. and Pierson, J. A. (2003), Photolylic reactors: similitudein Taylor-Couette and channel flows, AIChE J. 49:1285-1292, both ofwhich are incorporated by reference in their entirety as if fully setforth herein) considered a fast photolytic reaction and demonstratedthat optimum photoefficiencies could be achieved if the radiationpenetration depth were controlled in relation to the velocity, boundarylayer thickness. Their latter work also provided a scaling law for theyield in both Taylor-Couette and channel flows.

[0013] Thus, there is a need for systems and methods for the non-thermalprocessing of fluids.

[0014] There is another need for systems and methods for the non-thermalcontrol of micro-organisms in edible fluids.

SUMMARY OF THE INVENTION

[0015] Methods and systems for establishing Taylor-Couette flow in afluid are provided. Aspects of the methods and systems are useful forthe irradiation of microorganisms in the fluid. Exemplary methods andsystems incorporate Taylor-Couette flow in combination with a source ofradiation. Such a combination can provide more uniform radiationexposure to the fluid and components of the fluid.

[0016] One aspect provides a method and system for disinfecting a fluidthat includes introducing a fluid containing an organism, for example amicro-organism, into a reactor. The reactor typically includes a rotorhaving an outer wall. The rotor is housed within an outer cylinder. Theouter cylinder includes an inner annular wall. The outer wall of therotor and the inner wall of the outer cylinder define a first annularchannel or gap. The outer cylinder also includes an inlet and an outletin fluid communication with the annular channel or gap. Anelectromagnetic energy source is associated with the outer cylinder forirradiating the fluid in the annular channel or gap with ananti-microbial amount of electromagnetic energy. When the reactor isfilled with fluid to be sterilized or disinfected, the rotor speed iscontrolled to create laminar Taylor Couette flow (laminar vortices) inthe fluid in the annular channel or gap. The rotor speed can beregulated with a controller that can vary the rotation of the rotor toform laminar vortices in the fluid, for example inducing Taylor numbersin the fluid of about 40 to about 400. Controllers are known in the artand conventional controllers can be used so long as they can control therotor to induce laminar vortices or Taylor numbers of about 40 to about400. A further embodiment includes a second annular channel or gapinterior of the outer wall of the rotor providing a second annularchannel or gap for receiving the fluid. The first and second annularchannels being in communication with each other.

[0017] An exemplary method for irradiating a fluid includes inducingTaylor vortices in a fluid containing an organism, for example bygenerating a Taylor number in the fluid of between about 40 to about 400(representing laminar Taylor vortices); and irradiating the fluid withan anti-microbial amount of energy. The anti-microbial amount of energycan be ultraviolet light in an amount sufficient to kill or inhibitmicrobial growth in the fluid or render the fluid safe for humanconsumption. Suitable fluids include, but are not limited to, foodstuffssuch as beverages, milk, juice, soft drinks, or alcoholic beverages, andwaste water. In another embodiment, the ratio of the penetration depthof the energy to the velocity boundary layer thickness in the fluid isless than about 1, more preferably from about 0.5 to about 1.

[0018] Other systems, methods, features, and advantages of the presentinvention will be or become apparent to one with skill in the art uponexamination of the following drawings and detailed description. It isintended that all such additional systems, methods, features, andadvantages be included within this description, be within the scope ofthe present invention, and be protected by the accompanying claims.

BRIEF DESCRIPTION OF THE FIGURES

[0019] Many aspects of the invention can be better understood withreference to the following drawings. The components in the drawings arenot necessarily to scale, emphasis instead being placed upon clearlyillustrating the principles of the present invention. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views.

[0020]FIG. 1A is an illustration of Taylor vortices between twoconcentric cylinders. Inner cylinder rotating, outer cylinder at rest;d—width of annular gap; L—cylinder; R=cylinder radius.

[0021]FIG. 1B is an expanded view of Taylor vortices of FIG. 1A.

[0022]FIG. 2 is cross-sectional view of an exemplary embodiment of asystem for disinfecting or sterilizing a fluid including Taylor-Couettereactor.

[0023]FIG. 3 is a cross section of an exemplary Taylor-Couette reactorshowing symmetric and grouped irradiating lamp configurations.

[0024]FIG. 4 is a cross section of another embodiment of the presentinvention.

[0025]FIG. 5 is a diagram of a square reaction channel.

[0026]FIG. 6 is a line graph showing E. coli inactivation versus Taylornumber.

[0027]FIG. 7 is a line graph showing E. coli inactivation versus flowrate for various Taylor numbers. Ta=0 corresponds to flow betweenconcentric cylinders.

[0028]FIG. 8 is a line graph showing E. coli inactivation versus flowrate for symmetric and grouped lamp configurations. Ta=0 corresponds toflow between concentric cylinders.

[0029]FIG. 9 is a line graph showing E. coli inactivation versus flowrate for symmetric and grouped lamp configurations. Ta=100 correspondsto Taylor-Couette flow.

[0030]FIG. 10 is a line graph showing fractional E. coli inactivationversus UV dosage.

[0031]FIG. 11 is a line graph showing fractional E. coli inactivationversus dimensionless UV dosage for Taylor-Couette flow; n is thecorrection factor for the effects of the concentration boundary layer; mis the ratio of the average fluid UV intensity-to-the intensity at thequartz lamp surface; I_(o) is the average UV intensity at the lampsurface; K is the inactivation rate constant for E. coli.

[0032]FIG. 12 is a line graph showing fractional E. coli inactivationversus dimensionless UV dosage for Taylor-Couette flow (Ta=100). Theflow between concentric cylinders (Ta=0) and channel flow. Parametersare the same as in FIG. 11.

[0033]FIG. 13 is a line graph showing the percent change in outlettriiodide concentration versus the ratio of radiation penetration depthto velocity boundary layer thickness.

DETAILED DESCRIPTION

[0034] Embodiments of the present disclosure provide methods and systemsfor producing Taylor-Couette flow in a fluid. The fluid can be exposedto an energy source, for example an electromagnetic energy source suchas an ultraviolet light emitting lamp or other non-thermal energysource. Suitable UV lamps emit radiation in the range of about 200-400nm, preferably about 200-280 nm. The exposure of the fluid to the energysource can also catalyze a chemical reaction in the fluid or incomponents of the fluid. One embodiment provides a system and method ofirradiating a fluid in the absence of a catalyst. Additionally,irradiating the fluid with energy can kill or inhibit the growth oforganisms such as microorganisms, in the fluid. The term “organism”includes single and multicellular animals, viruses, protozoa, bacteria,fungi, pathogens, and the like.

[0035] In one embodiment, the flow characteristics of the fluid approachthat of plug flow but with a residence time that is uncoupled from thehydrodynamics or boundary layer characteristics. For example, oneexemplary system of the present invention includes an inner cylinderthat rotates within a stationary but larger outer cylinder as shown inFIG. 2 (Schlichting, H. (1979) Boundary Layer Theory, 7^(th) Ed.McGraw-Hill Book Co, NY). At low rotation rates a laminar, hydrodynamicconfiguration called Taylor-Couette flow is established consisting of asystem of circumferential vortices within the annular fluid gap. Thelatter constitutes a spatially periodic flow that is the hydrodynamicequivalent to cross flow over a tube bank or lamp array. These vorticesprovide radial mixing, reduce the boundary layer thickness and areindependent of the axial flow rate and thus the fluid residence time. Anadditional feature of the rotating design is the repetitive exposure ofthe fluid parcels to a minimum number of energy sources, for examplelamps, which substantially reduces the maintenance requirements. Thisrepetitive exposure also provides a cummulative exposure to radiationmore efficiently and effectively than the application of a single dose.A further embodiment provides systems and methods for irradiating afluid by inducing laminar vortices in the fluid, for example by inducingfluid Taylor numbers in the range of about 40 to about 400. Laminarvortices can be formed in the fluid by introducing the fluid into thedisclosed reactors, for example a reactor having a rotor within a hollowcylinder.

[0036] An exemplary reactor is shown in FIG. 2. The reactor includesrotor 205 positioned within an inner hollow of an outer cylinder 240. Anannular fluid gap 215 is formed between the inner cylinder of rotor 205.When the rotor rotates within the inner hollow of outer cylinder 240,Taylor-Couette flow is produced in the fluid within annular fluid gap215. The circumferential vortices 110 produced in the fluid causeparcels in the fluid to rotate as shown in FIG. 1. The rotation of theparcels permits the parcels to be repeatedly exposed, for example, to anenergy source 220. To maximize the exposure of energy, such asultraviolet light, to the parcels, a reflector 225 can be placed aroundthe exterior surface of energy source 220 to redirect scattered energyinto the fluid. The reflector can be made of any reflective materialincluding metals such as aluminum, tin, silver, glass, or a conventionalmirror. The outer cylinder typically has walls 210 composed of materialthat enables energy such as ultraviolet light to pass therethroughwithout an appreciable loss of energy due to absorption, refraction, orreflection. Suitable wall material includes quartz, glass, and syntheticpolymers, and may include any transparent medium.

[0037] Fluid enters the reactor via inlet 235, which is optionallypositioned at the base of outer cylinder 240. When rotor 205 is actuatedto begin rotating, Taylor-Couette flow is established. Fluid exits thereactor through outlet 230, optionally positioned at or near the top ofouter cylinder 240. The fluid can be any fluid including water,solutions, bodily fluids such as blood and the like, wastewater,effluent, wash water, and other waste water, or fluid foodstuffsincluding, but not limited to milk, juice, soft drinks, nutrient drinks,diet supplements, and alcoholic drinks etc. The fluid can be irradiatedby the energy source to facilitate chemical reactions in or with thefluid. Alternatively, irradiation of the fluid with energy from energysource 220 can serve to disinfect or sterilize the fluid. In oneembodiment, the irradiation energy is not in the form of heat.Embodiments of the present invention advantageously preserve theactivity of endogenous nutrients and enzymes in the fluid by usinganti-microbial amounts of non-thermal energy.

[0038] In another embodiment, at least one energy source 220 ispositioned tangentially to the outer cylinder wall 210. Suitable energysources include electromagnetic energy sources including microwaveenergy sources, ultraviolet light sources, sound wave sources, visiblelight sources, infra-red light sources, X-ray sources, gamma raysources, electron sources, atomic and sub-atomic particle sources, andthe like. FIG. 3A illustrates another exemplary embodiment of thereactor having a plurality of energy sources 220 positioned equidistantaround the outer cylinder 210. It will be appreciated that the energysources can be placed in any position around the annular fluid gap 215such that the energy emitted from the energy source 220 is directed intothe fluid in the annular fluid gap 215. FIG. 3B shows a plurality ofenergy sources 220 positioned opposite inlet 235.

[0039]FIG. 4 is a cross-sectional side view of still another embodimentof the present disclosure. In this embodiment, fluid enters the reactorthrough inlet 450 which is in fluid communication with an annularchannel 405. Inner annular channel 405 is in fluid communication withinner hollow 445. The reactor includes rotor 405 having an annularchannel 440 between an outer wall 410 and an inner cylinder 415. Rotor405 is housed or positioned within outer cylinder 240 such that theouter wall 410 of rotor 405 separates annular channel 405.

[0040] Outer cylinder 455 includes an inner annular wall 420 defining acircular hollow 445 for receiving inner cylinder 415 of rotor 405. Outerannular wall 460 defines annular channel 405 between outer annular wall460 and inner annular wall 420. Annular channel 405 receives outer wall410 of rotor 405. Annular wall 420 also separates annular channel 440when rotor 405 is positioned within outer cylinder 455. Fluid traversesthrough the annular channels and exits through outlet 430. Outlet 430 isoptionally positioned at the base of outer cylinder 455, for example inthe center of the base of outer cylinder 455 and opposite inner cylinder415. As the fluid traverses the annular channels, it is moved throughmultiple circumferential vortices exposing the fluid and particles inthe fluid to energy source 425. The design illustrated in FIG. 4 hasthree continuous fluid channels of equal length. This design allows forthe same number of vortices as a design having a single annular channelthree times the height as one of the channels of FIG. 4. The design ofFIG. 4 allows for a shorter rotor and reactor. Alternatively, two ormore annular channels can be provided.

[0041] Energy source 425 can be integral with annular walls 460, 410,420, or a combination thereof. Alternatively, energy source 425 can beremovably affixed to annular walls 460, 410, 420, or a combinationthereof or can form all or part of the walls. Energy from energy source425, such as ultraviolet light, can irradiate fluid as the fluidtraverses annular channels 405 and 440. Taylor vortices 110 formed inthe annular channels when the rotor is actuated cause the fluid andcomponents in the fluid to rotate as shown in FIG. 1 and increase theexposure of the fluid and components of the fluid to energy source 425.

[0042] The effects of flow rate, energy source location and cylinderrotation rate were considered for the inactivation of bacteria, forexample Escherichia coli. These results are compared with similar datain a conventional channel. Details of the correlation of the data arealso provided based on assumed inactivation kinetics and a plug flowreactor material balance. The latter analysis also introduces a newcorrection factor that accounts for the important boundary layereffects.

[0043] Another embodiment provides a Taylor-Couette reactor thatprovides excellent liquid surface renewal for the application ofelectromagnetic waves to chemical processing. The photoefficiency ofsuch processes is affected by the penetration depth of radiation intothe fluid relative to the velocity boundary layer thickness. Thesecondary flow caused by the presence of laminar vortices decreases theboundary layer thickness so that the dosage of radiation issubstantially increased for fluids with large radiation absorptivities.In another embodiment, the maximum photoefficiencies occur when theradiation penetration depth is equal to the boundary layer thickness.

[0044] Materials and Methods

[0045] Bacterial Culture

[0046] The Escherichia coli was obtained from the American Type CultureCollection, culture number 15597 (Manassas, Va.), The E. coli culturewas grown and maintained on tryptic soy agar (TSA; Difco Laboratories)and tryptic soy broth (TSB; Difco Laboratories). E. coli was asepticallyrehydrated using plates containing ATTC medium 271 agar at 37° C. for 24hours. Colonies were transferred to agar slants and refrigerated at 4°C. For each experiment, colonies were aseptically transferred to atest-tube containing 10 mL Acumedia 7164A Tryptic Soy Broth. Test-tubeswere placed in a Fisher Versa-Bath-S Model 224 temperature waterbath for24 hr (37° C. and 30 rpm agitation rate). One mL of broth solution wasdiluted to 1-liter deionized water to obtain the 10⁶ CFU/mL influent.

[0047] Wastewater

[0048] To mimic the bacterial load in wastewater, simulated wastewaterwas spiked with 10⁶ CFU/mL of the indicator organism Escherichia coli.The wastewater was sampled and E. coli colonies were enumerated ontryptic soy agar in order to determine E. coli survival. To simulatewastewater, bentonite which is a colloidal silica of specific gravity ofabout 2.0 was added to establish a total suspended solids (TSS)concentration and turbidity, with full transmittance (FT) values no lessthan 55%, turbidity less than 2 to 3 NTU, and TSS less than 5 mg/L.

[0049] Taylor-Couette Flow

[0050] A Taylor vortex column was constructed of 4.6 cm internaldiameter, fused quartz stator (Vycor) with a teflon rotor of 3.8 cmdiameter by 13 cm in length as shown in FIG. 2. The resulting annulargap width d was 0.4 cm. The inlet consisted of one 6 mm tube located 13mm from the bottom of the reactor. The irradiated holdup volume withinthe annular gap was 16.2 ml. Flow rates were varied from 13.1 to 136.8ml/min. with a positive displacement pump. Four cold cathode, lowpressure mercury UVC lamps with effective lengths of 3.1 cm [GilwayTechnical Lamp. 2001. catalog #169.] were positioned equidistant aroundthe outer quartz stator. In a second configuration the lamps weregrouped 180 degrees from the inlet such that adjacent lamps wereseparated by a distance of approximately 2 mm as shown in FIG. 3B.

[0051] Lamps were surrounded with an aluminum reflector 225 as shown inFIG. 2. Lamp output (mW) was determined with an International LightIL1471A germicidal radiometer system (IL1400A monitor andSEL240/QNDS2/TD sensor) providing a spectral range of 185-310 nm and ameasurement range of 33 μW/cm² to 330 mW/cm². Lamp intensity (mW/cm²)was measured after lamps were energized for 20-minutes. When all fourlamps were placed on the sensor with an aluminum reflector background,the intensity for the sensor area was recorded as 4.85 mW/cm². Theintensity for all four lamps was further recorded as 4.0 mW/cm² at 1 cmfrom the sensor surface. The intensity of radiation for each lamp(wavelength˜254 nm) was therefore rated at about 1 mW/cm at one cm fromthe lamp center.

[0052] The angular rotation of the rotor was controlled by a permanentmagnet DC motor providing Taylor numbers over a range from 0<Ta<1000where Ta=[Ud(d/R)^(1/2)]/ν. Here, U=ωR is the rotor surface velocity,the angular frequency to ω=2πf, f is the rotor frequency, R is the rotorradius, d is the gap width and ν is the kinematic viscosity of thefluid.

[0053] Channel

[0054] A continuous flow reactor channel 500, 18.5 cm in length,including two PVC flow straighteners at both ends was constructed from abronze 2×2 cm ID square. Centered in the channel 520 was a fused quartzcapillary tube 510 as shown in the cross section of FIG. 5. The quartztube 510 holds one cold cathode, low pressure, mercury UVC lamp 515 witha total effective irradiated length of approximately 7.8 cm. Theintensity of radiation for the lamp (wavelength of about 254 nm) wasabout 1 mW/cm² at 1 cm from the center.

[0055] The irradiated volume of the reactor was 28.6 ml and the flowrates covered a range of values from 10<q<40 ml/min. The reactorReynolds number covered the range 6<Re<25 for the indicated flow ratesproviding fully developed laminar flow in the cross sectional area. Thecross sectional area of the channel is A_(c)=3.9 cm² with a hydraulicdiameter of d_(h)=1.52 cm. An estimate of the laminar film thickness isδ=d_(h)/4=0.38 cm that corresponds to the distance to the centerline ofthe asymmetric cross section.

[0056] Plug Flow Reactor

[0057] The following analysis is an adaptation of that presented bySeverin et al. (Severin, B. F. et al. (1984) Kinetic modeling of UVdisinfection of water. Inactivation kinetics in a flow-through UVreactor, J WPCF. 56:164-169) who considered a completely mixedflow-through reactor. Here, we consider a plug flow geometry also ofannular design with a radiation source I_(o) at radius r_(o) along theaxis. The kinetics of inactivation are assumed to be first order withrespect to both the surviving organism density and the light intensity.Thus, the local disinfection rate R becomes

R=KI(r)N(r,x)   (1)

[0058] where

[0059] R=disinfection rate (organisms/cm³-sec)

[0060] K=rate constant (mW-sec/cni⁻²)⁻¹

[0061] I(r)=radiation intensity at radius r, and

[0062] N(r,x)—surviving organism density at radius r and axial positionx (organisms/cm³).

[0063] From Lambert's law for a radiation source of infinite length, oneobtains

I(r)=(r _(o)I_(o) r)exp(−E(r−r ₀))   (2)

[0064] where I_(o) is the radiation intensity at the quartz tube surfaceof radius r_(o), E=2.3A and A is the solution absorbance.

[0065] A local material balance for the surviving organism concentrationin an ideal plug flow reactor can be approximated in the form

q(dN)=−KN(x)I(r)dV   (3)

[0066] where we have assumed that N is a constant with radius. Here, qis the volume flow rate and V=π(r_(f) ²−r_(o) ²)L is the volume of thereactor and dV=27πrdrdx. Substitution of Eq. (2) into Eq. (3) andintegrating over r_(o)<r<r_(f), one obtains

dN/N=−mKI_(o) τdx/L   (4)

[0067] where N=N_(o) at x=0 and τ=V/q is the retention time. Thus, theoutlet concentration of surviving organisms becomes

N_(f)/N_(o)=exp(−mKI_(o)τ).   (5)

[0068] The dimensionless factor m in Eq. (5) is the ratio of the averagelight intensity in the reactor to the intensity at the surface of thequartz tube as derived by Severin et al. (Severin, B. F. et al. (1984)Kinetic modeling of UV disinfection of water. Inactivation kinetics in aflow-through UV reactor, J WPCF. 56:164-169) where

m=2r _(o)[1−exp(−E(r _(f) −r _(o))]/[E(r _(f) ² −r _(o) ²)].   (6)

[0069] It should be noted that for transparent fluids or E<1.0,m≅2r_(o)/(r_(o)+r_(o)).

[0070] If the concentration of surviving organisms N is not constantwith radius and a concentration boundary layer exists, then the argumentof the exponent of Eq. (5) would be reduced by a factor n<1.0. This isthe result of a reduced N in the local disinfection rate of Eq. (1) nearthe irradiated wall where the radiation intensity is the largest. Thus,one obtains

N_(f)/N_(o)=exp(−nmKI_(o)τ)   (7)

[0071] where n is an empirical constant that is independent of axialdistance for fully developed flow. Similar arguments were made in thestudy of photolytic reactions for such laminar plug flow geometries byForney and Pierson (Forney, L J. and Pierson, J A. (2003b), Photolylicreactors: similitude in Taylor-Couette and channel flows, AIChE J.49:1285-1292) which is incorporated herein in its entirety.

EXAMPLE 1 Taylor Number

[0072] Values for the inactivation of E. coli in the Taylor column wererecorded at increasing rotation rates up to roughly 300 rpmcorresponding to a Taylor number of 1000. The data shown in FIG. 6indicate a minimum of a 4-log reduction in surviving E. coli in units ofcolony forming units per ml or cfu/ml at a value of Ta=100 or roughly 30rpm (˜0.5 Hz). Although the value of Ta=100 is somewhat above thecritical value of Ta=41 for the onset of laminar Taylor vortices, Ta=100represented an incremental reduction of roughly 1 or 2-logs in cfu/mlcompared to other values of Ta with comparable flow rates as shown inboth FIGS. 6 and 7. At Ta=400 the vortices become turbulent and theresidence time distribution of the fluid broadens such that thecharacteristics of the Taylor column approach that of a completely mixedflow-through reactor. For values of 41<Ta<400 in the laminar range thereactor characteristics approach that of ideal plug flow with decreasingTa.

[0073] As indicated in FIG. 6 the optimum rotation rate is in thelaminar range of Ta. At higher rotation rates the bentonite is probablyforced to the outer stator surface which in turn absorbs the applied UVradiation. All data recorded in the experiment constitute the average ofat least two measurements of surviving E. coli for fixed operatingconditions. The error bar for the data point at the minimum in FIG. 6indicates the values for two independent measurements of E. coli. Theremaining data with the same error or uncertainty of roughly 10² cfu/mlper point was insignificant compared to the larger concentrations of E.coli on the log plot. Also recorded in FIG. 6 are the influentconcentrations of E. coli along with the expected error. The lattererror was determined by measuring the E. coli concentrations both beforeand at the conclusion of the experiments.

EXAMPLE 2 Flow Rate

[0074] Values of E. coli inactivation were recorded at increasing flowrates for three values of the Taylor number Ta=0, 100 and 120. Asindicated in FIG. 7 the inactivation levels decreased with higher flowrates for all values of Ta since the radiation dose ∝1/q where q is thevolumetric flow rate through the reactor. A value of Ta=100 provides thelargest inactivation rates for all recorded flow rates. Significantly,the plot also indicates an increase of over 2-logs for E. coliinactivation compared to simple flow through concentric cylinders (Ta=0)for moderate flow rates of 20 to 40 ml/min.

EXAMPLE 3 Lamp Symmetry

[0075] The effects of lamp location on inactivation were measured andthe data are recorded in FIGS. 8 and 9. FIG. 8 with no rotation or Ta=0demonstrates that channeling of the pathogens occurs between concentriccylinders when the lamps are grouped on the side of the reactor oppositethe fluid inlet.

[0076] For the symmetrical case of equidistant lamp location and atTa=100, FIG. 9 illustrates that an improvement of over a 1-log reductionin surviving organisms was again observed compared to the groupedgeometry for moderate flow rates between 20<q<60 ml/min. Moreover, theimprovement was somewhat less than 1-log at higher flowrates q>60 ml/minat lower photon dosages. One concludes that there is a significant lossof photons from both reflection and transmission through multiple lampsin close proximity,

EXAMPLE 4 Dosage

[0077] The inactivation of E. coli was measured for the channel and thedata are compared in FIG. 10 to the results taken with the Taylor columnat Ta=0 and 100. In FIG. 10 the UV dosage was computed based on theaverage radiation intensity within the fluid times the fluid residencetime. The value of m defined by Eq. (6) that represents the ratio ofaverage intensity within the fluid-to-the quartz surface value wasestimated from the approximation m=2r_(o)/(r_(o)+r_(f))=0.42 for lowfluid absorbance where r_(f) is equal to the radius of a circle with thesame cross sectional area as the square channel in FIG. 5. Thecorresponding values of m for the annular gap in the Taylor column wereestimated to be m=1.0 since the lamps were located outside the gap withphoto reflection inward toward the rotor.

[0078] The lamp intensity I_(o) in units of mW/cm² at the quartz tubesurface for the channel in FIG. 5 was computed from the lamp length andtube diameter. To compute I_(o), the total mW output from the 7.8 cmeffective lamp length was divided by the quartz tube surface area.Similarly, to compute the average light intensity I₀ of the insidesurface of the quartz stator in the Taylor column, the total lamp outputin mW for 4 lamps with an effective length of 3.1 cm per lamp wasdivided by the total surface area computed from the inside diameter ofthe quartz stator (length of 3.1 cm). The intensity of radiation forboth the channel and the Taylor column were based on an assumedabsorption of 6% for the quartz tube (GE 124) and 27% for the quartzstator (Vycor Coming 7913), respectively.

[0079] The results in FIG. 10 indicate more than a 3-log reduction inthe inactivation of E. coli with Taylor-Couette flow compared to aconventional channel at moderate flow rates of 20<q<40 ml/min. Theseconclusions are based on an equal radiation dosage in units of mJ/cm²within the fluid.

EXAMPLE 5

[0080] One of the major problems that one must contend with during thecontinuous use of UV reactors is the maintenance requirement of bothcleaning the numerous lamp surfaces from fouling and replacement ofdefective lamps. The use of Taylor-Couette flow provides repetitivecontact of fluid parcels with a minimum number of lamps. For example, inone embodiment described herein operating at Ta=100, with four lamps anda flow rate of 20 ml/min, a given fluid parcel will make roughly 25revolutions before reaching the outlet. Therefore, with four lamps perrevolution, a parcel of fluid therefore makes contact with theequivalent of 100 lamps as it passes through the Taylor column.

[0081] The optimum inactivation data for Ta=100 with the Taylor columncan be replotted in the form suggested by Eq. (7). The inactivation rateconstant for E. coli or K=0.89 cm²/mW-s that appears in the independentvariable nmKI_(o)τ was substituted from the batch inactivation data from(Severin, B. F. et al. (1984) Kinetic modeling of UV disinfection ofwater. Inactivation kinetics in a flow-through UV reactor, J WPCF.56:164-169). The remaining value of the boundary layer, correctionfactor n can be estimated by comparison with the data. The resultingplot is shown in FIG. 11 which is data replotted from FIG. 10 with avalue of n=0.28 in Eq. 1 that places the theory through the first sixdata points. As illustrated in FIG. 11, all of the fractionalinactivation data appear to conform to the model of a plug flow reactorwith the exception of those data taken at the low flowrates near q=20ml/min on the left of FIG. 10. These latter data are subject to both theeffects of the centrifugal forces leading to an increase in thebentonite concentrations near the transparent stator surface and togravitational settling of the silica colloid at the inlet passage.

[0082] In a similar fashion, all of the data of FIG. 10 were replottedin FIG. 12 with estimates of the boundary layer, correction factor n foreach case as shown in the figure caption. Again, all of the data appearto conform to the plug flow model. It is interesting to note thatestimated values of n in FIG. 11 appear to decrease with increasingboundary layer thickness. The latter observation conforms to the earlierwork of Forney, L. J. and Pierson, J. A. (2003), Photolylic reactors:similitude in Taylor-Couette and channel flows, AIChE J. 49:1285-1292which suggests that the yield from photolytic reactions in fullydeveloped laminar reactors n∝1/δ where δ is the velocity boundary layerthickness or that n∝1/δ in Eq. (7).

[0083] Table 1 shows a comparison with the empirical values of n used inFIG. 12 with the expression n=0.023/δ. The empirical values of n werechosen in FIG. 12 and Table 1 such that there were an equal number ofdata points both above and below the theory. Moreover, in Table 1 thevalues of the velocity boundary layer thickness 5 were taken fromForney, L. J. and Pierson, J. A. (2003), Photolylic reactors: similitudein Taylor-Couette and channel flows, AIChE J. 49:1285-1292 where 8 wasestimated to be dh/4 for both the channel and the case of flow between aconcentric cylinders (Ta=0) where dh is the hydraulic diameter. Thevalue of 5 for the case Ta=100 was estimated to be on the order ofTa^(−1/2) (Forney, L. J., and Pierson, J. A. (2003) Optimum photolysisin Taylor-Couette flow, AIChE J. 49:727-733).

[0084] The common problems of non-uniform radiation levels andconcentration boundary layer effects are largely eliminated in UVreactors with the use of Taylor-Couette flow that is the hydrodynamicequivalent to cross flow over a tube bank (Baier, G. et al. (1999).Prediction of mass transfer in spatially periodic systems, Chem. Eng.Sci. 54:343) or for this application a lamp array. Moreover, therepetitive exposure of fluid parcels to a small number of lampsdecreases maintenance requirements. Over a 3-log reduction in theinactivation of E. coli under the best conditions was demonstratedcompared to a conventional channel with the same radiation dosage.Moreover, greater than a 2-log reduction was evident compared to flowthrough concentric cylinders.

[0085] The inactivation data for three reactor geometries ofTaylor-Couette flow and flow between either concentric cylinders or asquare channel are correlated with the assumption of plug flow. Inparticular, the effects of non-uniform radiation levels are accountedfor by integration across the fluid channel as done in the past but anew correction factor is introduced that is inversely proportional tothe velocity boundary layer thickness to account for the effects of aconcentration boundary layer. TABLE 1 Prediction of Boundary LayerCorrection Factor-n n empirical Flow Geometry Boundary Layer Thickness -δ(cm) 0.023/δ (FIG. 11) Taylor-Couette 0.08 0.28 0.28 Ta = 100Concentric 0.2 0.11 0.09 Cylinders Ta = 0 Channel 0.38 0.06 0.06

EXAMPLE 6 Photochemistry

[0086] Fast UV photolysis of aqueous iodide producing triiodide was alsoinvestigated. Concentrated KI solutions are optically opaque atwavelengths of 254 nm and act as photon counters. UV absorption byiodide leads to an aqueous or solvated electron via a chargetransfer-to-solvent reaction and the formation of an excited iodine atomThe essential reactions are listed below,

I⁻ +hv→I+e ⁻  (8)

I+e ⁻→I⁻  (9)

2I*+I⁻→I₃ ⁻  (10)

[0087] As noted, the UV-induced formation of triiodide is potentiallylimited by the back reaction of Eq. (9). The quantum yield for triiodideis significantly increased, however, by the addition of potassiumiodate. In the presence of iodate, scavenging of the bulk electronoccurs and the following additional reaction is proposed

IO₃ ⁻ +e ⁻+2H₂O→IO⁻+H₂0₂+OH*+OH⁻  (11)

[0088] The yield of the triiodide photoproduct is easily monitored byspectrophotometry at either 350 or 450 nm depending on theconcentration. The quantum yield of φ=0.75 mol./einstein is relativelyconstant with either temperature or reagent iodide concentrations. Withthe addition of a borate buffer (pH 9.25) to minimize thermal oxidation,stock solutions of 0.6 M KI and 0.1M KIO₃ with the borate buffer arestable and insensitive to ambient light in the visible spectrum. Radialmass transfer in Taylor-Couette flow has been documented in terms of aSherwood number Sh of the form

ShαTa^(1/2)Sc^(1/3)   (12)

[0089] where the Taylor number

Ta=(ωRd/ν)(dR)^(1/2).   (13)

[0090] The indicated exponents in Eq. (12) were determined previously bya number of experiments and also confirmed by the recent numericalpredictions. The torque coefficient CM for Taylor-Couette flow is of theform

C_(M)=2M/(πρω² R ⁴ h)αTa^(−1/2)   (14)

[0091] for the range of Taylor numbers Ta_(c)<Ta<400 where the criticalTaylor number Ta_(c)=41 indicates the onset of laminar vortices. Here,the moment M=τ(2πR²) and τ is the shear stress on the rotor.

[0092] Equations (12) and (14) suggest that the transport coefficientsin laminar, Taylor-Couette flows are correlated by a Chilton-Colbumanalogy of the form

J _(D) =Sh/(TaSc^(1/3))=C_(M)/2   (15)

[0093] For the values 40<Ta<400 and the Schmidt number Sc=ν/D>1, Theseconclusions are consistent with laminar and heat transfer correlationson a spinning disc but with Ta replaced by the Reynolds number based onthe disc angular velocity and diameter.

[0094] Consider now a laminar boundary layer with a linear velocity andconcentration profile (film model) on the surface of a Taylor-Couetteflow (Ta>Ta_(c)) Since the mass transfer coefficient k_(c)αD/δ_(c), andthe Sherwood number

Shαk_(c)d/D   (16)

[0095] where δ_(c) is the concentration boundary layer thickness, d isthe gap width and D is the solute molecular diffusivity, one obtains

Shαd/δ_(c)α(d/δ)(δ/δ_(c)).   (17)

[0096] Since a boundary layer analysis confirmed by experiment suggestsδ_(c)/δαSh^(1/3), one obtains a ratio of characteristic reactor lengthd-to-velocity boundary thickness

d/δαTa^(1/2)   (18)

[0097] for Ta>Ta_(c).

[0098] Attempts to obtain Eq. (18) by stretching the characteristiclengths d or δ for a boundary layer on a flat plate by a factor of(d/R)^(1/2) were unsuccessful. There is some evidence, however, that theSherwood number ShαTa^(1/2)Sc^(1/3)(d/R)^(0.17) from the mass transferexperiments of Holeschovsky and Cooney but, again, the exponentmagnitude of 0.17 is inconsistent with the attempted boundary analysisthat would suggest larger values.

[0099] Fast photochemical reactions must occur near transparent reactorwalls. The thickness of the reaction layer, however, is not confined toa fraction of the velocity boundary thickness, but rather to theradiation penetration depth. The latter depth, in fact, can exceed boththe boundary thickness or characteristic reaction dimension depending onthe absorbance of the reacting solution.

[0100] Since the solution absorbance is defined by

A=AεC   (19)

[0101] where the intensity of radiation is I/I_(o)=10^(−A), ε is theextinction coefficient, C is the absorbing species and A, is theradiation depth, the reaction layer is therefore confined to a layer onthe order of

AαI/εC.   (20)

[0102] An additional dimensional parameter is the maximum possibleconcentration of photochemical product formed. The latter is equal tothe product of the number of photons introduced into the reactor and thequantum efficiency of the reaction. The maximum concentration of productformed is thus

Cm=nI_(o) A ₁ φ/γq   (21)

[0103] where n is the number of lamps, I_(o), is the intensity ofradiation [W/cm2], A₁ is the area of a single lamp, φ is the reactionquantum efficiency [mol product/einstein], q is the reactor volume flowrate and γ[J/einstein] is the conversion factor from a mol of photons tojoules of energy.

[0104] Dimensional arguments suggest that the concentration ofphotochemical product formed C_(ω)is of the form

C_(ω)/C_(i)(I)αf(Cm/C_(i)(I), λ/δ)   (22)

[0105] provided the Taylor number Ta>0 where C_(i)(I) is theconcentration of reactant iodide in the inlet stream. Simplifying Eq.(22) somewhat since a mass balance implies C_(ω)αCm, one obtains

Cω/C_(i)(I)αCm/C_(i)(I)[f(λ/δ)].   (23)

[0106] Defining Co as the product concentration with no rotation, onenow obtains an expression which isolates the effects of rotation in theform of the dimensionless quantity

(Cω−Co)/Co=f(λ/δ)   (24)

[0107] Another embodiment provides a Taylor vortex column having abronze rotor 3.43 cm in diameter by 5 cm in length centered within afused quartz beaker with an inside diameter of 4.1 cm providing a gapwidth of d=0.334 cm. The holdup volume (irradiated) was 12 ml with arange of flow rates between 15<q<50 ml/min. Five cold cathode, lowpressure mercury UVC lamps with effective lengths of 3.1 cm werepositioned around the quartz beaker and surrounded by an aluminumreflector with an over 90% reflectivity of UV radiation. The intensityof radiation for each lamp (wavelength ˜254 run) was rated at 1.7 mW/cm2at the lamp surface providing a range of power input from 0.033 W to0.164 W depending on the number of lamps engaged.

[0108] A solution of 0.6 M potassium iodide (KI) and 0.1 M potassiumiodate (KIO₃) buffered (pH 9.25) with borate was pumped through theTaylor column. The absorbance of triiodide at the outlet was measured ateither 350 or 450 run for low or high concentrations, respectively,depending on the number of lamps engaged or liquid flow rate. The rpm ofthe rotor, controlled by a permanent magnet DC motor, was varied between0<rpm<75 providing a Taylor number covering the range 0<Ta<200.

[0109] The triiodide absorbance as expected, clearly indicated a largeincrease of roughly 60% for Taylor numbers Ta>Ta_(c) where the lowerlimit of Ta_(c)=40 corresponds to the onset of Taylor vortices at lowaxial Reynolds numbers. Since the cross sectional area for the flowwithin the gap is 4 cm², the axial Reynolds number was Re<10 for allexperiments and thus had no effect on the critical Ta_(c).

[0110] Plug Flow Reactor

[0111] When the Taylor number Ta>Ta_(c) and laminar vortices are presentwithin the Taylor column, the flow can best be described asapproximating that of an ideal plug flow reactor. Assuming a zero orderrate expression at steady-state. one obtains

udC/dx=r   (25)

[0112] where the constant rate[mol/liter-s]

r=nI_(o) A _(l) φ/γV   (26)

[0113] and V is the holdup volume of the reactor Thus, the concentrationof triiodide formed from Eq. (25) with dx/u=dV/q is

C(I₃)=βrV/q   (27)

[0114] where the factor β<<1 accounts for both the loss of input radiantenergy to liquid heating and surface absorption and the effects of backreactions from triiodide to iodide depleting the product as describedlater.

[0115] Normalized plots of Eq. (23) for the outlet triiodideconcentration for increasing flow rates at fixed rpm (Ta=100) and thestandard stock solution (0.6 M iodide) where Cm is defined by Eq (14)show that the photo efficiency of the reactor is not high (<30%) so thataxial variations in the iodide reactant and thus the radiationpenetration depth are small consistent with the analysis.

[0116] Effects of Rotation

[0117] The effects of rotation are isolated by comparing the productconcentration at fixed Taylor numbers Ta>Ta_(c) with the product formedat zero rpm or Ta=0. Because of the large surface-to-volume ratio forthe reactor, one would expect a considerable enhancement in themagnitude of the transport coefficients without vortices. A nearlyconstant 70% improvement in product yield occurs for all Ta>Ta_(c)

[0118] Percentage increase in reaction product at fixed Ta=100 forvarious values of the radiation dosage were obtained by engaging one tofive UV lamps and changing the flow rate between 16 and 32 ml/min. Thereis some scatter in the data possibly due to channeling through thereactor for the Ta=0 case, since the reactor inlet and outlet werelocated on the same side but 45° apart. Thus, the sequence of lamps inthe circumferential direction was varied for several experiments withthe same total power input leading to the indicated scatter. However, itis apparent from the data that the concentration of product formed dueto rotation is independent of the dosage of radiation supplied assuggested by Eq. (24).

[0119] Optimum Rotation

[0120] The similarity law proposed by Eq. (24) was tested by varying thereactant concentration, that is, the concentration of iodide fed to thereactor inlet. Since the absorbance A=λεC_(i)(I) is 200 for a 0.6 M KIand 0.1 M KIO₃ solution, the extinction coefficient e at a wavelength of254 nm was calculated to be ε=333 M⁻¹cm⁻¹. Setting the absorbance A=1that represents a radiation depth over which 90% of the UV photons areabsorbed, one calculates the radiation depth to be λ=1/εC_(i)(I).

[0121] The stock solution of 0.6 M KI and 0.1 M KlOs along with a seriesof additional solutions with KI and KIO₃ in the same ratio but dilutedby a factor of up to 100 were fed to the reactor. The product triiodideconcentration was measured at both Ta=0 and 100 for each inlet solution.The data show that the reaction yield is inhibited if the reaction layerlies within the velocity boundary layer or λ/δ<<1 (see FIG. 1B). Underthese circumstances the large concentration of I₃ ⁻ within the boundaryis reduced by the solvated electron e_(aq) ⁻ back to I⁻ via the reaction

e _(aq) ⁻+I₃ ⁻→I₂ ⁻+I⁻  (28)

[0122] and the product yield of K is diffusion limited.

[0123]FIG. 13 shows the percent change in outlet triiodide concentrationversus the ratio of radiation penetration depth to velocity boundarylayer thickness. If the reaction layer thickness is greater than thevelocity boundary layer or λ/δ>>1, the product I₃ ⁻ is formed throughoutthe gap and the advantages of the circulating vortices are substantiallyreduced. It should be noted that the left data point in FIG. 13corresponds to a reaction layer that is 15% of the velocity boundarythickness where the latter is 10% of the gap width d. In contrast, theright data point in FIG. 13 represents a radiation depth that is 150% ofthe gap width d. At the optimum operating conditions λ/δ=1 one obtains amaximum 150% increase in the product concentration. Under the latterconstraint if

λ/δ=Ta^(1/2)/(dεC_(i)(I))   (29)

[0124] setting λ/δ=1, one obtains an optimum frequency fop Hz ofrotation equal to

f _(op)=(ν2π)(dR)^(1/2)ε²C_(i) ²(I)

[0125] Scale-Up

[0126] An efficient UV reactor requires multiple exposure of thepathogen to a fixed number of lamps positioned around the reactorcircumference. The number of cycles of the pathogen around the axis ofthe reactor as the pathogen passes from inlet to outlet is N where

N=ft_(r)

[0127] and f is the rotor frequency (cycles/sec) and t_(r) is the fluidresidence time or

t _(r)=V/q=πDdh/q

[0128] Here, h is the rotor length, d is the gap width, D (=2R, see FIG.1A) is the rotor diameter, q is the fluid flowrate and V is the volumeof fluid within the annular gap. The number of cycles N can be rewrittenin the form

N=Ta(D/2d)^(1/2) νh/q

[0129] Thus, for fixed Taylor number Ta and gap width d such that theratio of radiation penetration depth-to-boundary layer thickness λ/δ isa constant and for fixed fluid properties ν, one obtains

NαD^(1/2)h/q

[0130] Thus, scale-up of the reactor to larger rotor diameters D andlonger rotors h is achieved for fixed N if

qαD^(1/2)h

[0131] It should be emphasized that the above-described embodiments ofthe present invention, particularly, any “preferred” embodiments, aremerely possible examples of implementations, merely set forth for aclear understanding of the principles of the invention. Many variationsand modifications may be made to the above-described embodiment(s) ofthe invention without departing substantially from the spirit andprinciples of the invention. All such modifications and variations areintended to be included herein within the scope of this disclosure andthe present invention and protected by the following claims.

What is claimed is:
 1. A fluid reactor comprising: an annular wallhaving an inside wall; a rotor having an outer wall placed within theouter annular wall, the inside wall of the outer annular wall and theouter wall of the rotor forming an annular fluid channel; a fluid inletin the outer annular wall in communication with the annular fluidchannel; a fluid outlet in the outer annular wall also in communicationwith the annular fluid channel; a rotor control controlling the rotationof the rotor to provide laminar vortices in fluid in the annular fluidchannel; and an energy source for irradiating the fluid in the annularfluid channel with an anti-microbial amount of energy.
 2. The fluidreactor of claim 1, wherein the energy source provides electromagneticenergy.
 3. The fluid reactor of claim 2, wherein the electromagneticenergy irradiates fluid in the reactor.
 4. The fluid reactor of claim 3,wherein the electromagnetic energy is provided in an anti-microbiallyeffective amount.
 5. The fluid reactor of claim 1, wherein the energysource is a lamp for providing ultraviolet light.
 6. The fluid reactorof claim 1, wherein Taylor-Couette flow is established in fluid withinthe reactor when the rotor is rotated.
 7. The fluid reactor of claim 1,wherein the Taylor-Couette flow comprises a plurality of circumferentialvortices within the annular fluid channel.
 8. The fluid reactor of claim1, wherein the outer annular wall is transparent.
 9. The fluid reactorof claim 1, wherein the outer annular wall comprises an energy source.10. The fluid reactor of claim 1, further comprising a reflector aroundthe outside of the outer annular wall.
 11. A fluid reactor comprising:an outer cylinder; a rotor having a first annular channel between anouter wall and an inner cylinder, wherein the rotor is housed within theouter cylinder, the outer cylinder having: an inner annular walldefining a circular hollow for receiving the inner cylinder of therotor, and an outer annular wall defining a second annular channelbetween the outer annular wall and inner annular wall for receiving theouter wall of the rotor; an inlet in fluid communication with the secondannular channel; and an outlet in fluid communication with the circularhollow.
 12. The reactor of claim 11, wherein the outer cylinder furthercomprises an energy source.
 13. The reactor of claim 12, wherein theenergy source provides electromagnetic energy.
 14. The reactor of claim13, wherein the electromagnetic energy irradiates fluid in the reactor.15. The reactor of claim 14, wherein the electromagnetic energy isprovided in an anti-microbially effective amount.
 16. The reactor ofclaim 12, wherein the energy source is a lamp for providing ultravioletlight.
 17. The reactor of claim 11, wherein Taylor-Couette flow isestablished in fluid within the reactor when the rotor is rotated withinthe outer cylinder.
 18. The reactor of claim 11, wherein theTaylor-Couette flow comprises a plurality of circumferential vorticeswithin the first and second annular channels.
 19. The reactor of claim11, wherein the outer wall of the rotor is transparent.
 20. The reactorof claim 11, wherein the inner and outer annular walls of the outercylinder comprise an energy source.
 21. The reactor of claim 1, furthercomprising a reflector around the outside of the outer annular wall. 22.A method for disinfecting a fluid comprising: providing a fluid reactorhaving a rotor having an outer wall placed within the outer annularwall, the inside wall of the outer annular wall and the outer wall ofthe rotor forming an annular fluid channel; a fluid inlet in the outerannular wall in communication with the annular fluid channel; a fluidoutlet in the outer annular wall also in communication with the annularfluid channel; controlling the rotation of the rotor to provide laminarvortices in fluid in the annular fluid channel; introducing a fluidcomprising a micro-organism into the fluid reactor; and irradiating thefluid in the annular fluid channel with an anti-microbial amount ofenergy.
 23. The method of claim 22, further comprising the step ofestablishing Taylor-Couette flow in fluid within the reactor by rotatingthe rotor within the outer cylinder.
 24. The method of claim 23, whereinthe Taylor-Couette flow comprises a plurality of circumferentialvortices within the annular fluid channel.
 25. The method of claim 22,wherein the energy source is a lamp for providing ultraviolet light. 26.The method of claim 22, wherein the fluid comprises wastewater.
 27. Themethod of claim 22, wherein the fluid comprises an edible fluid.
 28. Themethod of claim 27, wherein the edible fluid comprises milk, fruitjuice, or a beverage.
 29. The method of claim 22, wherein the ratio ofpenetration depth of the energy to the velocity boundary layer is lessthan about
 1. 30. The method of claim 22, wherein the ratio ofpenetration depth of the energy to the velocity boundary layer is fromabout 0.5 to about
 1. 31. The method of claim 22, wherein the fluidreactor comprises a plurality of fluid annular channels.
 32. A method ofdisinfecting a fluid comprising: inducing Taylor vortices in a fluidcomprising an organism, wherein the Taylor number of the fluid isbetween about 40 to about 400; and irradiating the fluid with ananti-microbial amount of energy.
 33. The method of claim 32, wherein theanti-microbial amount of energy is about 400 J/m².
 34. The method ofclaim 32, wherein the Taylor number is from about 75 to about
 125. 35.The method of claim 32, wherein the organism comprises bacteria, fungi,protozoa, viruses, or a combination thereof.
 36. The method of claim 32,wherein the energy is electromagnetic energy.
 37. The method of claim32, wherein the fluid comprises wastewater.
 38. The method of claim 32,wherein the fluid comprises an edible fluid.
 39. The method of claim 38,wherein the edible fluid comprises milk, fruit juice, or a beverage. 40.The method of claim 39, wherein the ratio of penetration depth of theenergy to the velocity boundary layer is less than about
 1. 41. Themethod of claim 32, wherein the ratio of penetration depth of the energyto the velocity boundary layer is from about 0.5 to about 1.